Field of the Invention:
The invention relates to a method for determining a layer orientation for a 2D layer image that is to be generated from 3D image data of an anatomical object in a patient's body.
Patients' 3D image data or, as the case may be, 3D data records is/are increasingly being generated in the field of medical imaging for 3-dimensionally imaging a respective anatomical object in the patient's body. Examples of such anatomical objects include organs, bones, and joints in the patient's body. 3D image data is usually visualized in the form of 2D layer images. Multiplanar reformatting (MPR) is an instance of what is known. Layers of a 3D data record are here displayed as 2D layer images, with the layer orientation being defined—at least in the case of planar layers or locally—by a projection direction perpendicular to the layer. There is established, as a rule, the layer, which is also to take a curved course, for example. For simplicity's sake, reference is here repeatedly made to the projection direction, although the invention can be applied also to selecting the position of layers having any shape.
For representing 3D image data using MPR there are defined standards which, depending on the specific organ in the patient's body or his/her ailment or, as the case may be, on the object being imaged, establish the respective layer orientation requiring to be shown as the default orientation (and hence the projection direction) for 2D layer images obtained from the 3D image data. That applies in particular to bone imaging when the anatomical object is accordingly a bone or, as the case may be, joint in the patient's body. The default orientation's position relative to the (standardized) object is thereby established for all layer representations of any patients.
In certain radiological applications, computed tomography for instance, the required or, as the case may be, correct layer orientation is produced automatically in the image data: That is possible because the patient always lies in a defined position in the recording device when the 3D image data is being recorded. The image data or, as the case may be, the object being imaged therefore has a defined spatial position or, as the case may be, orientation in a given coordinate system of the 3D image data.
Intraoperative applications for generating 3D image data such as, for instance, 3D C-arc imaging are, though, also known. The initial situation is different here as there is broad scope for freely selecting the patient's respective position relative to the imaging system. Thus the anatomical object's position or, as the case may be, orientation in the 3D image data is not predefined or, as the case may be, is not comparable or standardized for different recordings.
For 3D image data of such kind it is hence first necessary to determine an appropriate layer orientation or, as the case may be, imaging direction, for example an optimal layer orientation or, as the case may be, default orientation or one specified according to medical standards for certain joints.
It is known that the surgeon or surgical assistant first has to process the intraoperatively recorded 3D image data manually, which is to say as a rule has to turn and move it to determine and present the optimal or, as the case may be, standardized layer orientation or position. That takes extra operating time with possible changing between a sterile and non-sterile area, and it also requires experienced personnel. In other words the layer orientation for the 2D layer images is here established by hand based on a subjective consideration and assessment of the 3D image data.